Cartridges are commonly used in the medical and pharmaceutical field for the modification of the content of medical or biological fluids such as blood, blood plasma, blood serum, ultrafiltrate, dialysate, irrigation fluid and infusion fluid. Usually, a cartridge contains particles in various forms that react with fluid, which is pumped through an inlet in the cartridge. Cartridges can be used during dialysis to adsorb impurities from a patient's blood. Other cartridge uses include; (2) exchanging substances from fluid against others contained in the particles; (3) modifying substances in fluid by catalytic or enzymatic reactions; and (4) releasing substances into fluid.
During adsorption, molecules of medical or biological fluid flow through the cartridge between the particles and diffuse in all directions. Some molecules are diffused in the direction of a particle and are absorbed. Diffusion time is largely dependent upon particle size such that large diameter particles require a much longer diffusion time for complete adsorption. On the other hand, the use of small diameter particles causes an increase in a hydraulic pressure drop between the cartridge inlet and outlet. For practical purposes such as power requirements, this pressure drop must be limited, especially when a plurality of cartridges are used in series.
In view of the above, there is a need for a cartridge design that reduces diffusion time with the use of small particles, but does not create a substantial pressure drop between the cartridge inlet and cartridge outlet.